1. Field of the Invention
This invention relates to novel absorbent materials, a process for preparing these materials and absorbent articles such as diapers or sanitary napkins containing the absorbent. More specifically, the absorbent materials comprise polysaccharides which have been cross-linked with aluminum, titanium or zirconium cross-linking agents.
2. Technology Description
Many attempts have been described in the patent literature to prepare absorbent materials, i.e. materials which are capable of absorbing many times their weight of water or various body fluids.
The following list is representative of United States patents which have issued in this area: U.S. Pat. No. 3,528,421 (disposable absorbent underpad for hospital patients or similar product, hydrous calcium silicate chemical absorbent); U.S. Pat. No. 3,563,243 (absorbent pads such as diapers, underpads and the like-hydrophilic polymer absorbent); U.S. Pat. No. 3,669,103 (absorbent products containing a hydrocolloidal polymeric absorbent lightly cross-linked polymer such as poly-N-vinyl-pyrrolidone, polyvinyltoluenesulfonate, poly-sulfoethyl acrylate, and others); U.S. Pat. No. 3,686,024 (water absorbent articles coated with a water-swollen gel such as cross-linked partially hydrolyzed polyacrylamide); U.S. Pat. No. 3,670,731 (absorbent dressing using water soluble hydrocolloidal composition); U.S. Pat. No. 3,783,872 (absorbent articles such as diapers, and the like using insoluble hydrogels as the absorbing media); U.S. Pat. No. 3,898,143 (disposable absorbent articles using poly(ethylene oxide) and at least one other water soluble polymer co-crosslinked by high energy irradiation); U.S. Pat. No. 4,055,184 (absorbent pads for disposable diapers, sanitary napkins, bandages or the like using solid, finely-divided mixture of a hydrolyzed starch polyacrylonitrile graft copolymer in acidic form and a non-irritating and non-toxic water-soluble basic material); U.S. Pat. No. 4,069,177 (water absorbing and urine stable step-wise grafted starch-polyacrylonitrile copolymers); U.S. Pat. No. 4,076,663 (water absorbing starch resins); U.S. Pat. No. 4,084,591 (absorber for blood made from filaments of a lower alkyl or a lower hydroxyalkyl substituted cellulose ether).
In U.S. Pat. No. 3,903,889 the patentee describes as an absorbent composition for use in absorbent products a guar gum which is modified with borate anion in an amount sufficient to complex the gel formed from the hydration of guar gum alone. Specifically, the patentee teaches introducing borate ion into the absorbent product in the form of an essentially water insoluble borate-release agent in which the free borate ion is released slowly to the absorbent system and only after the aqueous liquid sought to be absorbed by the product has entered the product itself. It is suggested that the modified guar gum can absorb up to at least 20 times its weight of water to produce a relatively dry non-sticky and inert gel.
U.S. Pat. Nos. 4,333,461 and 4,624,868 are directed to absorbent materials which comprise borate cross-linked polysaccharides. The enabled polysaccharides are guar gum and its derivatives.
U.S. Pat. No. 4,952,550 is directed to particulate absorbent materials which are carboxylated cellulosic materials. More specifically, the materials are cellulosic base materials which are reacted with a cross-linking agent and a hydrophobicity agent. Preferred cross-linking agents include metals such as aluminum, iron or chromium. Similarly, Research Disclosure 349,296 suggests the use of aluminum cross-linked cellulose gums as absorbent materials.
Other known absorbent materials include those derived from acrylic polymers and those derived from amino acids.
Except for the polyacrylates and starch grafted acrylates, with respect to their application for absorbing or holding fluids such as in diapers, sanitary napkins, bandages, gloves, sporting goods, pet litter and the like the absorbent materials and absorbent products described in these patents have not been commercially acceptable. Such problems as insufficient absorbing capacity, insufficient rigidity of the swollen gel, breakdown of the gel structure upon contact with saline fluids, incompatibility with absorbent articles, still exist.
U.S. Pat. Nos. 4,605,736 and 4,677,201 are directed to cross-linking polygalactomannans with a titanium based cross-linking agent. The in situ cross-linking reaction is performed in an aqueous environment and the polygalactomannan is not recovered. These aqueous systems are suggested for use in oil recovery.
U.S. Pat. No. 4,959,464 is directed to the production of aluminum cross-linked derivatized polygalactomannans. The resulting products are suggested for use as thickening agents which readily hydrate under alkaline pH conditions.
Despite the above teachings, there still exists a need in the art for novel compositions which have functionality as absorbent materials.